Voice and Swallowing Dysfunction in Neurofibromatosis 2

Schwannomatosis: a Realm Reborn: year one

PURPOSE OF REVIEW

In 2022, an international consensus recommendation revised the nomenclature for neurofibromatosis type 2 ( NF2 ) and Schwannomatosis (SWN), now grouped under the umbrella term Schwannomatosis, and defined new diagnostic criteria.

RECENT FINDINGS

This review describes the molecular criteria for diagnosis of schwannomatosis and the subsequent diagnosis strategy, while setting out the most recent advances in our understanding of the natural history, pathology, molecular biology and treatment of schwannomatosis-associated tumors, including schwannomas, meningiomas and ependymomas.

SUMMARY

Somatic mutation screening should become a new standard for the diagnosis of NF2 -, LTZTR1 -, SMARCB1 - and 22q-schwannomatosis to discriminate those conditions. Constitutional events in NF2 -Schwannomatosis have a major influence on disease severity and justifiably motivate ongoing efforts on gene replacement therapy research. On the other hand, underlying mechanisms of disease severity and associated pain remain largely unknown in non- NF2 -SWN and independent of germline mutation. Research efforts therefore focus on pain relief in ongoing trials and the discovery of new molecular mechanisms underlying schwannoma tumorigenesis/pain/neuropathies.

The Neurofibromatoses

BACKGROUND

Neurofibromatosis of types 1 and 2 (NF1, NF2) and schwannomatosis are the diseases that make up the neurofibromatosis spectrum. With respective incidences of 1 in 3000, 1 in 33 000, and 1 in 60 000 births, they form part of the group of rare tumor-suppressor syndromes. They give rise to a greater tumor burden for the nervous system than any other type of neoplastic disease. New approaches to symptomatic treatment are emerging.

METHODS

This review is based on articles retrieved by a selective literature search on the pathogenesis, diagnosis, and treatment of the neurofibromatoses.

RESULTS

NF1 and NF2 are monogenic diseases, while the genetics of schwannomatosis is complex. The three entities are clinically and pathophysiologically distinct. An important aspect of their tumor biology is the alternation of growth phases and growth pauses. Correlations between genotypes and phenotypes are variable, while new mutations and genetic mosaics are common. Ninety-nine percent of patients with NF1 have six or more café-au-lait spots by the age of 12 months; 90-95% of patients with NF2 develop bilateral vestibular schwannomas. In schwannomatosis, pain is the most prominent symptom; two-thirds of those affected develop spinal schwannomas. The severity and prognosis of these disorders are not closely correlated with the radiological findings; rather, neurologic deficits, malignant transformation, and psychosocial stress are of greater clinical importance. Advances in knowledge of pathophysiology have led to the development of targeted treatment approaches. Examples include the off-label treatment of vestibular schwannomas with bevacizumab and of plexiform neurofibromas with MEK inhibitors.

CONCLUSION

Patients with neurofibromatoses need individualized care. They should be treated in centers of expertise where interdisciplinary consultation is available and new types of pharmacotherapy can be provided.

Neurofibromatosis type 2 and related disorders

PURPOSE OF REVIEW

Neurofibromatosis type 2 (NF2) is a schwannoma predisposition syndrome, alongside schwannomatosis related to germline LZTR1 and SMARCB1 pathogenic variants. This review highlights their overlapping phenotypes, new insight into NF2 phenotype and treatment outcomes.

RECENT FINDINGS

Mosaic NF2 is more prevalent than previously thought. Use of next-generation sequencing and tumour testing is needed to differentiate mosaic NF2 and schwannomatosis. Developing NF2 phenotypic insights include vasculopathy with brainstem infarction and vessel stenosis; focal cortical dysplasia in severe phenotypes; swallowing/speech difficulties and continued debate into malignancy in NF2. Proposed are: use of visual evoked potentials to monitor optic nerve sheath meningioma; potential routine magnetic resonance angiogram in adolescence and a genetic score to cohort patients with similar pathogenic_variants, for natural history/treatment outcome studies. Cohort studies found survival analysis to hearing loss and unilateral visual loss in severe mutation groups was 32 and 38 years; active management gave better outcomes than surveillance in spinal ependymoma; gamma knife, bevacizumab and hearing preservation surgery maintained or improved short-term hearing in selected patients, and gamma knife had a good long-term tumour control in mild patients with small tumours.

SUMMARY

Further long-term outcome studies are needed comparing similar severity patients to allow informed decision making.

A Prospective Evaluation of Swallowing and Speech in Patients with Neurofibromatosis Type 2

Objective  Neurofibromatosis type 2 (NF2) patients report that swallowing and speech problems significantly affect their quality of life, but the etiology of these phenomena is poorly understood. Swallowing and speech deficits may arise due to the neuropathy of involved nerves, due to posterior fossa tumor growth, or as iatrogenic effects from neurosurgical procedures to remove these tumors. This study aims to identify the natural history of swallowing and speech deficits in an NF2 cohort and to characterize the factors that may lead to those deficits. Methods  Subjects ( n  = 168) were enrolled in a prospective, longitudinal study of NF2 with yearly imaging and clinical exams. The patients completed a self-reported questionnaire that included responses regarding subjective swallowing and speech dysfunction. A formal speech-language pathology evaluation and modified barium swallow (MBS) study (reported as American Speech-Language Hearing Association [ASHA] swallowing independency score from 1 through 7) was obtained when a speech/swallowing deficit was reported on the questionnaire. Results  Of the 168 enrolled subjects, 55 (33%, median age = 31 years) reported subjective speech and/or swallowing deficits. These patients underwent one ( n  = 37) or multiple ( n  = 18) MBS studies during 44.8 ± 10.4 months follow-up. During MBS, a majority demonstrated near-normal swallowing (ASHA score >6, 82%), and no evidence of aspiration (aspiration/laryngeal penetration score = 1, 96%). Prior to initial MBS consultation, 38 (69%) patients had undergone relevant neurosurgical procedures. In those with recent (<1 week) posterior fossa surgery ( n  = 12), 2 (17%) patients had severe dysphagia and high aspiration risk on postoperative MBS. Both of these patients recovered to functionally independent swallowing status. Unilateral ( n  = 10) or bilateral ( n  = 6) tongue deficits unrelated to previous history suggestive of hypoglossal nerve injury were detected on clinical examination. There was a correlation between the presence of dysarthria and tongue deficits and tumors associated with the hypoglossal canal noted on imaging. Conclusion  A large proportion of patients with NF2 report speech and swallow deficits that are not evident on objective measurements. We also found hypoglossal neuropathy unrelated to prior surgical interventions. Our findings suggest that swallowing and speech problems in NF2 are associated with lower cranial nerve neuropathy, some due to compressive effects of posterior fossa tumors. Adaptation over the course of the disease allows for the compensation of these deficits and subsequent normal findings on objective testing.